docs: def ensure_unique_obs_ids_in_wide_data(obs_id_col, wide_data):
      """
      Ensures that there is one observation per row in wide_data. Raises a
      helpful ValueError if otherwise.
  
      Parameters
      ----------
      obs_id_col : str.
          Denotes the column in `wide_data` that contains the observation ID
          values for each row.
      wide_data : pandas dataframe.
          Contains one row for each observation. Should contain the specified
          `obs_id_col` column.
  
      Returns
      -------
      None.
      """
      if len(wide_data[obs_id_col].unique()) != wide_data.shape[0]:
          msg = "The values in wide_data[obs_id_col] are not unique, "
          msg_2 = "but they need to be."
          raise ValueError(msg + msg_2)
  
      return None